Alloy steel



Feb; 25, 1947.

L G. SELMI rm 2,416,649

ALLOY STEEL Filed March 4, 1942 3 Sheets-Sheet 2 m TEN: ILE STREN 5TH RED. AREA M 60 PR ORTLONAL' LIMIT EFFECT ONE HOUR DRAW 0N PH (SIC L PROPERTIES 40 (OLD DRAW 1 BAR hFTEa Y 19.5%cow zoucnou 3O 91 I2 ELOIGATION k 0 2 0 4 4$o 5 0 8?0 We '0 AWY EMPERAT RE E FIGZ . -I/VVNTOR Lac/0N0 a. 5501/ and CLARE/{6E 1.. nut/man a? A TTORNEYS Feb. 25, 1947. S LM, E AL 2,416,649,

ALLOY STEEL Filed March 4, 1942 s sheets-sh e't s //V VENTORS Patented Feb. 25, 1947 I ALLOY STEEL Luciano G. Sclmi, Detroit, and Clarence'L. Altenburger, Dearborn, Mich assignors to Great Lakes Steel Corporation, Ecorse, Mich., a corporation of Delaware Application March 4, 1942, sci-la n. 433,404 7 4 Claims. (01. 148-31) l This invention relates, as indicated, to alloy steels but has reference more particularly to alloy steels of the so-called low alloy types,

qualities, long fatigue life, ductility for deep.

drawing, and extremely high impact properties at normal as well as at sub-zero temperatures. Basically it is a low alloy steel, attaining high qualities and in which valuable alloying elements, and particularly those of present strategic importance, such as silicon, chromium and zirconium, are held to a minimum.

Another desirable characteristic of this steel when carburlzed is that the structure has no massive cementite network, such as constitutes a weakness of the hypereutectoid case produced in the carburizing of other steels. Further, we have found that both nickel and silicon prevent high carbon concentration in the case even when fairly large content of chromium is present. Same is true in respect to the presence of molybdenum when used as in the above named patents and co-pending application, Serial No. 433,384.

The invention sought to be covered by this present application and as hereinafter claimed is a steel having balanced relationships of the constituents such that, within the limits of sectional thicknesses, andunder treatmentconditions herein given, results are accomplished which have not been possible in previoushi h tensile, low alloy steels.

Other' objects will become apparent from the following description. The steel in addition to iron, contains the fol- 2 lowing elements intended in practice to be within the ranges specified:

Per cent Carbon .08-.30 Manganese .30-.'15 Silicon .60-.90 Chromium .30-.75 Zirconium i .06-.20 Sulphur '.03-max. Phosphorous .03-max. A preferred steel within the foregoing range is one having he following analysis:

Per cent Carbon .13 Manganese .66 Silicon .80 Chromium 1 .54 Zirconium .06-.l3 variable Sulphur .025 Phosphorous .020 This particular steel, when used in fas rolled, or normalized condition, or when stress relieved for high tensile steel fabrication, possesses a resistance to fatigue andnotched bar values at the strength levels of 50,000 p. s. 1. minimum yield strength and 70,000 p. s. 1. minimum tensile strength common to low alloy high tensile steels, and greater than those heretofore available.

sizing temperatures; (b) comparative freedom from blue brittleness anclhence freedom from strain aging even in the. normalized or as rolled conditions, and (0) good notched bar particular steel are its excellent-'weldability as well as the ability to be cold formed into various diflicult shapes.

The effects of various conditioning heat treatin the above table at varying carburizing tem- .peratures. The time at temperatures given being eight hours and the fumace'being cooled. frm the carburizingtemperature.

The following Table III givesprope'rties of a similar steel as rolled and, normalized at the temperatures given, i.'e. 1575 F. to .1850 F. and as listed, the yield point, tensile (or ultimate) strength, elongation in 2, 4, 6, and 8 inches and reduction of area.

A ments after hot rolling bar of the analyses indi- T m cated to various physical properties appear. in 6 Elongmon the drawings and tables herein given. 1 Yield Tensile I Red A Fig. 1 is a chart showing physical properties at strength diflerent drawing temperatures. v

Fig. 2 is a chart showing eflect of drawing on M 11 00..- 500 73,500 42 an 29.1 25. physical prop rties. i Noi l i g: 72 500 42 28 1 27 5 4 Fig. 3 is a micro-photograph showing grain 1600. 500 1000 42 34 2 2-3 structure and size of our steel when carburizedr. I 1950: 53.500 12.000 4; as 30.7 28.1 15.5 The following Table I gives physical properties 85 g g f% 33 23:2 Q of our steel as rolled finishing at temperatures 1800: 50,000 11,000 42 31.0 20.5 21.1 14. from 1000" F. to 1650 F. producing '1 to 0 Mc- 15 Quaid Ehn grain size, according to the following Table II and Fig. 3. Table IV shows Carpy key hole impact strength Tm I at 75 F., on the longitudinal and transverse, at 2 30 F., at 0 F., minus 50 F., and at minus100 F. 0 Mn P 0 s1 01' Zr TABLE w .13 .51 .020 .020 .84 .50 .11 KBYPY test round finishing rolling temperatures 1000 112001050 F. 75 F. 32 F. 0 F. 9? 3 A u dgrain 1 15' s [Ema Y.P. Y.P. Y.P. Y.P. Y.P. 7 Longitudinal 67. 7 04 60 63 41. 5 Elongation Transverse 48.5 45 41.5 35.5 24.00 Tensile 333 Red.A.

End quenched Rockwell C hardness of our steels Lo n dim of similar, analyses are given in the following I] u 72,475 53,000 52 a1 21 01.0 Tra sverse 71,000 50,200 40 34 25 58.6 Tables v and 35 Tom V n Hard ess R kw no E d a] I! 00 B Carbon analysis of carburized specimen at u qumhan temperature shown 40 c .14 m" 40 I gin .5 g g"... a5 mfi 1020 F. 11000 F. 1750" F. I 21 fi .85 1 a I II 0-o.005" Carbon %,1.05 Carbon 1.05 Carbon 1.21. z; 2 QUE-0,010 Carbon%, .90-- Carbon 1.00 Carbon 7 1.07. 1%" 010-0.015" Carbon%,.84.. Carbon ,.94 Carbon 1.05. 015-0020 Carbon%,.77 Carbon iil. Car'bon'7,.99. 0020-0.025".. Curbon%, .72.. Carbon ,.85.. Carbon j t). o.o25-o.03o"- 0115001191,, .05 CarbonpSL. Carbon ,.91. Turn. VI

.030-0.040" Carbon%,.57 Carbon .75.. Carbon .87. Grain size..." 56.". 'k w End quench analysis Ilardfigsgkggfikaeli C.

The analysis of this steel is as follows:

. I Per cent Carbon .12 -Manganese .66

Phosphorus .026 Sulphur .025 Silicon .85 Chromium .54 It should be noted that heating above the AC: Zirconium .13 00 point brings the physicals to almost the same value. v

The physical propertiescan be raised considerably bycold drawing. Cold drawing lowers the proportional limit but this can be raised considerably by a short draw, as shown in the accompanying drawing, Fig. 2, in which the eifect of a one hour draw onthe physical properties of cold drawn bar on a steel of approximately the preferred analysis after 19.5% cold reduction is graphically illustrated. 1

The weldability of this alloy steel is ally good. 1

For one bead weld the Rockwell B hardness when the parent metal is the Rockwell B exceptionhardness in the heat aflected zone will not exin the heat affected zone in multiple bead welds.

\ Tear: VII I Plain and quench bar test 1" diameter x 3" long Rockwell C hardness Distance 16th" 20 40 43 44 44 51 as 40 42 44 a1 a0 a4 a1 40 49 24 30 a2 41 14 1a 20 21 so a ""12 15 14 a s "'"5 10 19 0 7- s s 15 0 0 s e 14 5 0 7 1 11 5 5 0 '0 11 Grain size.- Fine Fine Fine Fine 1 Quench. temp degrees 1,630 1,630 1,630 1,575

described will under carburizing treatment with solid, liquid or gaseous cementing medium produce an hypereutectoid case practically free of cementite network as shown in microphotograph, Fig. 3. Such hypereutectoid case free of cementite network is much stronger and more desirable in hard wearing surface such as required in gears, pinions, etc., which will spell on if the hypereutectoid case is made up work.

Having thus described our invention, the nature and scope thereof are defined in the apof cementite net-.

pended claims, it being understood that the particular relationships and ranges specified may be subject to slight or reasonable variation without departing from the spirit of our-invention.

We claim: v v

l. A case carburized-steel article formed from chromium carburizing steel containing as essential alloying elements. 0.1 to about 0.3 per cent of carbon, from about 0.5 to about 0.75 per cent of chromium, about0.6 to about 0.9 per cent of silicon, .06 to .20 per cent of zirconium, and substantially no nickel, and the remainder iron together with impurities and elements in amounts which do not adversely affect the, carburizing characteristics of the steel, and characterized by the carburized and hardened case being resistant to spalling and low in or substantially free from massive carbides.

2. A chromium-containing carburized steel article containing as essential alloying elements about 0.5 to about 0.75 per cent of chromium, about 0.6 to about 0.9 per cent of silicon, .06 to .20 per cent of zirconium, carbon from 0.1 toabout 0.3 per cent and man amount such that the steel is hardenableby heat treatment, and the remainder iron together with impurities and.

3. A nickel-free carburized steel article con taining as essential alloying elements from about 0.1 to about 0.3 per cent of carbon, about 0.5 to

about 0.75 per cent of chromium, about 0.6 .to about 0.9 per cent of silicon, .06 to .20 per cent of 4. A case carburized steel article formedirom chromium carburizingsteel containing as essential alloying elements. about 0.1 to about 0.3 per cent of carbon, about 0.5 to 0.75 per cent of chromium, about 0.6 to about 0.9 per cent of silicon, .06 to .20 per cent of zirconium, and the remainderiron together with impurities'and elements in amounts which do not adversely aifect the carburizing characteristics of the steel, and characterized by the carburized and hardened case being resistant to spalling and low in or substantially free from massive carbides.

LUCIANO G. SELMI. CLARENCE L. ALTENBURGER.

v anemone omen The following references are of record in the file of this patent:

UNITED sra'rzs mums Number 2 Name I Date 1 2,114,002 Kinzel -----.-1 Apr. 10.1230 2.250.505 Selmi July 20, 1941 2,102,434 Kinzei Mar. 20, 1022 

